Water-sensitive film containing thermoplastic polyurethanes

ABSTRACT

A film that contains a thermoplastic polyurethane and water-soluble polymer is provided. The film is both elastic and water-sensitive (e.g., water-soluble, water-dispersible, etc.) in that it loses its integrity over time in the presence of water. The dual attributes of elasticity and water-sensitivity may be achieved by reducing the tendency of the thermoplastic polyurethane and water-soluble polymer to form separate phases. Namely, phase separation may cause the elastomer to act as a barrier and limit the ability of the water-soluble polymer to contact water and thereby disperse. To minimize such phase separation, a variety of aspects of the film construction may be selectively controlled, such as the nature of the thermoplastic polyurethane and water-soluble polymer, the relative amount of each component, and so forth.

Related Applications

The present application is a continuation of U.S. Application Ser. No.12/120,260, filed on May 14, 2008, which is incorporated herein in itsentirety by reference thereto.

BACKGROUND OF THE INVENTION

Films are employed in a wide variety of disposable goods, such asdiapers, sanitary napkins, adult incontinence garments, bandages, etc.For example, many sanitary napkins have an adhesive strip on thebackside of the napkin (the napkin surface opposite to thebody-contacting surface) to affix the napkin to an undergarment and holdthe napkin in place against the body. Before use, the adhesive strip isprotected with a peelable release liner. Once removed, the peelablerelease liner must be discarded. Conventional release liners may containa film or paper coated with a release coating. Such release-coated filmsor papers, however, do not readily disperse in water, and as such,disposal options are limited to depositing the release liner in a trashreceptacle. Although disposing of conventional release liners in atoilet would be convenient to the consumer, it would potentially createblockages in the toilet.

Flushable films have been developed that are formed from awater-dispersible polymer. U.S. Pat. No. 6,296,914 to Kerins, et al.describes a water-sensitive film that may include, for instance,polyethylene oxide, ethylene oxide-propylene oxide copolymers,polymethacrylic acid, polymethacrylic acid copolymers, polyvinylalcohol, poly(2-ethyl oxazoline), polyvinyl methyl ether, polyvinylpyrrolidone/vinyl acetate copolymers, methyl cellulose, ethyl cellulose,hydroxypropyl cellulose, hydroxypropyl methyl cellulose, ethylhydroxyethyl cellulose, methyl ether starch, poly(n-isopropylacrylamide), poly N-vinyl caprolactam, polyvinyl methyl oxazolidone,poly(2-isopropyl-2-oxazoline), poly (2,4-dimethyl-6-triazinyl ethylene),or a combination thereof. Some of these polymers, however, are notthermoplastic and thus are not readily processed using thermoplasticfilm converting equipment. Further, these films are also not elastic andmay thus be limited in their use. In response to these and otherproblems, attempts have been made to form water-shrinkable films fromelastomeric and water-dispersible polymers. One such film is describedin U.S. Pat. No. 5,641,562 to Larson, et al. In one example, the film isformed that contains polyethylene oxide having a molecular weight ofabout 200,000 and an ethylene vinyl acetate copolymer. Although suchfilms are shrinkable, they nevertheless are not dispersible ordisintegratable in water so as to achieve complete flushability.Furthermore the films are not elastic.

As such, a need currently exists for an improved film that is bothelastic and water-sensitive in that it readily loses its integrity overtime in the presence of water.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, awater-sensitive elastic film is disclosed that comprises at least onewater-soluble polymer, at least one plasticizer, and at least onethermoplastic polyurethane synthesized from at least one polyol and atleast one organic diisocyanate. The water-soluble polymer has a weightaverage molecular weight of from about 10,000 to about 150,000 grams permole and a number average molecular weight of from about 1,000 to about80,000 grams per mole. The weight ratio of the water-soluble polymer tothe plasticizer is from about 1 to about 50 and the weight ratio of thewater-soluble polymer to the thermoplastic polyurethane is from about0.01 to about 3.0.

In accordance with another embodiment of the present invention, a methodfor forming a water-sensitive, elastic film is disclosed. The methodcomprises melt blending a composition that comprises at least onewater-soluble polymer, at least one plasticizer, and at least onethermoplastic polyurethane synthesized from at least one polyol and atleast one organic diisocyanate. The method also comprises extruding thecomposition to form a film.

Other features and aspects of the present invention are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, whichmakes reference to the appended figures in which:

FIG. 1 is a schematic illustration of one embodiment of a method forforming a film in accordance with the present invention;

FIG. 2 is a top view of an absorbent article that may be formed inaccordance with one embodiment of the present invention;

FIG. 3 is an SEM photograph of the film of Example 8; and

FIG. 4 is a graph showing the melt viscosity of plasticized Elvanol™51-05, Celvol™ 523S, Celvol™ 513, Desmopan™ DP9370A, and Estane™ 58245at various shear rates.

Repeat use of references characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS Definitions

As used herein, the terms “machine direction” or “MD” generally refersto the direction in which a material is produced. The term“cross-machine direction” or “CD” refers to the direction perpendicularto the machine direction. Dimensions measured in the cross-machinedirection are referred to as “width” dimension, while dimensionsmeasured in the machine direction are referred to as “length”dimensions.

As used herein, the terms “elastomeric” and “elastic” generally refer toa material that, upon application of a stretching force, is stretchablein at least one direction (such as the CD direction), and which uponrelease of the stretching force, contracts/returns to approximately itsoriginal dimension. For example, a stretched material may have astretched length that is at least 50% greater than its relaxedunstretched length, and which will recover to within at least 50% of itsstretched length upon release of the stretching force. A hypotheticalexample would be a one (1) inch sample of a material that is stretchableto at least 1.50 inches and which, upon release of the stretching force,will recover to a length of at least 1.25 inches. Desirably, thematerial contracts or recovers at least 50%, and even more desirably, atleast 80% of the stretched length.

As used herein the terms “extensible” or “extensibility” generallyrefers to a material that stretches or extends in the direction of anapplied force by at least about 50% of its relaxed length or width. Anextensible material does not necessarily have recovery properties. Forexample, an elastomeric material is an extensible material havingrecovery properties. A film may be extensible, but not have recoveryproperties, and thus, be an extensible, non-elastic material.

As used herein, the term “percent stretch” refers to the degree to whicha material stretches in a given direction when subjected to a certainforce. In particular, percent stretch is determined by measuring theincrease in length of the material in the stretched dimension, dividingthat value by the original dimension of the material, and thenmultiplying by 100.

As used herein, the term “set” refers to retained elongation in amaterial sample following the elongation and recovery, i.e., after thematerial has been stretched and allowed to relax during a cycle test.

As used herein, the term “percent set” is the measure of the amount ofthe material stretched from its original length after being stretchedand relaxed. The remaining strain after the removal of the appliedstress is measured as the percent set.

DETAILED DESCRIPTION

Reference now will be made in detail to various embodiments of theinvention, one or more examples of which are set forth below. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations may be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment, may be used on another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

Generally speaking, the present invention is directed to a film thatcontains a thermoplastic polyurethane and water-soluble polymer. Thefilm is both elastic and water-sensitive (e.g., water-soluble,water-dispersible, etc.) in that it loses its integrity over time in thepresence of water. The dual attributes of elasticity andwater-sensitivity may be achieved by reducing the tendency of thethermoplastic polyurethane and water-soluble polymer to form separatephases. Namely, phase separation may cause the elastomer to act as abarrier and limit the ability of the water-soluble polymer to contactwater and thereby disperse. To minimize such phase separation, a varietyof aspects of the film construction may be selectively controlled, suchas the nature of the thermoplastic polyurethane and water-solublepolymer, the relative amount of each component, and so forth. Forexample, thermoplastic polyurethanes are polar in nature and thus may begenerally compatible with water-soluble polymers (e.g., polyvinylalcohol), which are also polar in nature. Further, water-solublepolymers having a relatively low molecular weight and viscositytypically possess better melt compatibility with polar thermoplasticpolyurethanes. By carefully controlling the nature of the polymers usedto form the film, the present inventors have discovered that a film maybe formed that is generally free of distinct phases.

In this regard, various embodiments of the present invention will now bedescribed in more detail below.

I. Film Components

A. Thermoplastic Polyurethane

Thermoplastic polyurethanes are generally synthesized from a polyol,organic diisocyanate, and optionally a chain extender. The synthesis ofsuch melt-processable polyurethane elastomers may proceed eitherstepwise (e.g., prepolymer dispensing process) or by simultaneousreaction of all components in a single stage (e.g., one-shot dispensingprocess) as is known in the art and described in more detail in U.S.Pat. Nos. 3,963,656 to Meisert, et al.; 5,605,961 to Lee, et al.;6,008,276 to Kalbe, et al.; 6,417,313 to Kirchmeyer, et al.; and7,045,650 to Lawrey, et al., as well as U.S. Patent ApplicationPublication Nos. 2006/0135728 to Peerlings, et al. and 2007/0049719 toBrauer, et al., all of which are incorporated herein in their entiretyby reference thereto for all purposes.

A polyol is generally any high molecular weight product having an activehydrogen component that may be reacted and includes materials having anaverage of about two or more hydroxyl groups per molecule. Long-chainpolyols may be used that include higher polymeric polyols, such aspolyester polyols and polyether polyols, as well as other acceptable“polyol” reactants, which have an active hydrogen component such aspolyester polyols, polyhydroxy polyester amides, hydroxyl containingpolycaprolactones, hydroxy-containing acrylic interpolymers,hydroxy-containing epoxies, and hydrophobic polyalkylene ether polyols.Typically, the polyol is substantially linear and has two to three, andmore preferably two hydroxyl groups, and a number average molecularweight of from about 450 to about 10,000, in some embodiments from about450 to about 6000, and in some embodiments from about 600 to about 4500.Suitable polyether dials may be produced by, for example, reacting oneor more alkylene oxides having 2 to 4 carbon atoms in the alkyleneresidue with a starter molecule that contains two or more activehydrogen atoms in bound form. Exemplary alkylene oxides include ethyleneoxide, 1,2-propylene oxide, epichlorohydrin and 1,2-butylene oxide and2,3-butylene oxide. Exemplary starter molecules include water;aminoalcohols, such as N-alkyl-diethanolamines (e.g.,N-methyl-diethanolamine); and diols, such as ethylene glycol,1,3-propylene glycol, 1,4-butanediol and 1,6-hexanediol. Suitablepolyester diols may be produced from dicarboxylic acids (or derivativesthereof) having 2 to 12carbon atoms, preferably 4 to 6 carbon atoms, andpolyhydric alcohols. Exemplary dicarboxylic acids include aliphaticdicarboxylic acids, such as succinic acid, glutaric acid, adipic acid,suberic acid, azelaic acid and sebacic acid; aromatic dicarboxylicacids, such as phthalic acid, isophthalic acid and terephthalic acid; aswell as derivatives of such acids, such as carboxylic acid diestershaving 1 to 4 carbon atoms in the alcohol residue, carboxylic anhydridesor carboxylic acid chlorides. Examples of suitable polyhydric alcoholsinclude glycols with 2 to 10, preferably 2 to 6 carbon atoms, such asethylene glycol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, 1,10-decanediol, 2,2-dimethyl-1,3-propanediol,1,3-propanediol, and dipropylene glycol. Esters of carbonic acid withthe stated diols are also suitable, and particularly, those having 4 to6 carbon atoms, such as 1,4-butanediol or 1,6-hexanediol; condensationproducts of co-hydroxycarboxylic acids, such as ω-hydroxycaproic acid orpolymerisation products of lactones (e.g., optionally substitutedω-caprolactones). Preferred polyester diols include ethanediolpolyadipates, 1,4-butanediol polyadipates, ethanediol/1,4-butanediolpolyadipates, 1,6-hexanediol/neopentyl glycol polyadipates,1,6-hexanediol/1,4-butanediol polyadipates and polycaproplactones.

The organic diisocyanates may include aliphatic diisocyanates, such asethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,12-dodecanediisocyanate, 1,6-hexamethylene diisocyanate, mixtures thereof, etc.;cycloaliphatic diisocyanates, such as isophorone diisocyanate,1,4-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate,1-methyl-2,6-cyclohexane diisocyanate, 4,4′-, 2,4′- or2,2′-dicyclohexylmethane diisocyanate, mixtures thereof, etc.; and/oraromatic diisocyanates, such as 2,4- or 2,6-toluene diisocyanate,4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate,2,2′-diphenylmethane diisocyanate, naphthylene-1,5-diisocyanate,xylylene diisocyanate, methylene diphenyl isocyanate (“MDI”),hexamethylene diisocyanate (“HMDI”), mixtures thereof, etc.

The chain extenders typically have a number average molecular weight offrom about 60 to about 400 and contains amino, thiol, carboxyl, and/orhydroxyl functional groups. The preferred chain extenders are thosehaving two to three, and more preferably two, hydroxyl groups. As setforth above, one or more compounds selected from the aliphatic diolsthat contain from 2 to 14carbon atoms may be used as the chain extender.Such compounds include, for example, ethanediol, 1,2-propanediol,1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol,1,6-hexanediol, diethylene glycol, dipropylene glycol,1,4-cyclohexanediol, 1,4-dimethanolcyclohexane and neopentyl glycol,Diesters of terephthalic acid with glycols having 2 to 4 carbon atomsmay also be employed. Some examples of such compounds includeterephthalic acid bis-ethylene glycol and terephthalic acidbis-1,4-butanediol, hydroxyalkylene ethers of hydroquinone (e.g.,1-4-di(β-hydroxyethyl)hydroquinone), ethoxylated bisphenols (e.g.,1,4-di(β-hydroxyethyObisphenol A), (cyclo)aliphatic diamines (e.g.,isophoronediamine, ethylendiamine, 1,2-propylenediamine,1,3-propylenediannine, N-methyl-1,3-propylenediamine, andN,N′-dimethylethyiene-diamine), and aromatic diamines (e.g.,2,4-toluenediamine, 2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamineand 3,5-diethyl-2,6-toluenediamine, and primary mono-, di-, tri- ortetraalkyl-substituted 4,4′-diaminodiphenylmethanes).

In addition to those noted above, other components may also be employedto form the thermoplastic polyurethane. Catalysts, for instance, may beemployed to facilitate formation of the polyurethane. Suitable catalystsinclude, for instance, tertiary amines, such as triethylamine,dimethylcyclohexyl-amine, N-methylmorpholine, N,N′-dimethylpiperazine,2-(dimethylaminoethoxy)-ethanol, diazabicyclo[2.2.2]octane, etc. as wellas metal compounds, such as titanic acid esters, tin diacetate, tindioctoate, tin dilaurate or the dialkyltin salts of aliphatic carboxylicacids such as dibutyltin diacetate or dibutyltin dilaurate or othersimilar compounds. Still other suitable additives that may be employedinclude light stabilizers (e.g., hindered amines), chain terminators,slip agents and mold release agents (e.g., fatty acid esters, the metalsoaps thereof, fatty acid amides, fatty acid ester amides and siliconecompounds), plasticizers, antiblocking agents, inhibitors, stabilizersagainst hydrolysis, heat and discoloration, dyes, pigments, inorganicand/or organic fillers, fungistatically and bacteriostatically activesubstances, fillers, etc.

The thermoplastic polyurethane typically has a melting point of fromabout 75° C. to about 250° C., in some embodiments from about 100° C. toabout 240° C., and in some embodiments, from about 120° C. to about 220°C. The glass transition temperature (“T_(g)”) of the thermoplasticpolyurethane may be relatively low, such as from about −150° C. to about0° C., in some embodiments from about −100° C. to about −10° C., and insome embodiments, from about −85° C. to about −20° C. The meltingtemperature and glass transition temperature may be determined usingdifferential scanning calorimetry (“DSC”) in accordance with ASTMD-3417. Examples of such thermoplastic polyurethanes are available underthe designation DESMOPAN™ from Bayer MaterialScience and under thedesignation ESTANE™ from Lubrizol. DESMOPAN™ DP 9370A, for instance, isan aromatic polyether-based polyurethane formed from poly(tetramethyleneether glycol) and 4,4-methylenebis(phenylisocyanate) (“MDI”) and has aglass transition temperature of about −70° C. and a melting temperatureof from about 188° C. to about 199° C. ESTANE™ 58245 is likewise anaromatic polyether-based polyurethane having a glass transitiontemperature of about −37° C. and a melting temperature of from about135° C. to about 159° C.

B. Water-Soluble Polymer

The film also includes one or more water-soluble polymers. Such polymersmay be formed from monomers such as vinyl pyrrolidone, hydroxyethylacrylate or methacrylate (e.g., 2-hydroxyethyl methacrylate),hydroxypropyl acrylate or methacrylate, acrylic or methacrylic acid,acrylic or methacrylic esters or vinyl pyridine, acrylamide, vinylacetate, vinyl alcohol (hydrolyzed from vinyl acetate), ethylene oxide,derivatives thereof, and so forth. Other examples of suitable monomersare described in U.S. Pat. No. 4,499,154 to James, et al., which isincorporated herein in its entirety by reference thereto for allpurposes. The resulting polymers may be homopolymers or interpolymers(e.g., copolymer, terpolymer, etc.), and may be nonionic, anionic,cationic, or amphoteric. In addition, the polymer may be of one type(i.e., homogeneous), or mixtures of different polymers may be used(i.e., heterogeneous). In one particular embodiment, the water-solublepolymer contains a repeating unit having a functional hydroxyl group,such as polyvinyl alcohol (“PVOH”), copolymers of polyvinyl alcohol(e.g., ethylene vinyl alcohol copolymers, methyl methacrylate vinylalcohol copolymers, etc.), etc. Vinyl alcohol polymers, for instance,have at least two or more vinyl alcohol units in the molecule and may bea homopolymer of vinyl alcohol, or a copolymer containing other monomerunits. Vinyl alcohol homopolymers may be obtained by hydrolysis of avinyl ester polymer, such as vinyl formate, vinyl acetate, vinylpropionate, etc. Vinyl alcohol copolymers may be obtained by hydrolysisof a copolymer of a vinyl ester with an olefin having 2 to 30 carbonatoms, such as ethylene, propylene, 1-butene, etc.; an unsaturatedcarboxylic acid having 3 to 30 carbon atoms, such as acrylic acid,methacrylic acid, crotonic acid, maleic acid, fumaric acid, etc., or anester, salt, anhydride or amide thereof; an unsaturated nitrile having 3to 30 carbon atoms, such as acrylonitrile, methacrylonitrile, etc.; avinyl ether having 3 to 30 carbon atoms, such as methyl vinyl ether,ethyl vinyl ether, etc.; and so forth.

The degree of hydrolysis may be selected to optimize solubility, etc.,of the polymer. For example, the degree of hydrolysis may be from about60 mole% to about 95 mole%, in some embodiments from about 80 mole% toabout 90 mole%, and in some embodiments, from about 85 mole% to about89mole%. Examples of suitable partially hydrolyzed polyvinyl alcoholpolymers are available under the designation CELVOL™203, 205, 502, 504,508, 513, 518, 523, 530, or 540 from Celanese Corp. Other suitablepartially hydrolyzed polyvinyl alcohol polymers are available under thedesignation ELVANOL™50-14, 50-26, 50-42, 51-03, 51-04, 51-05, 51-08, and52-22 from DuPont.

The water-soluble polymers employed in the present invention generallyhave a low molecular weight. For example, the water-soluble polymers mayhave a number average molecular weight (“M_(n)”) ranging from about1,000 to about 80,000 grams per mole, in some embodiments from about5,000 to about 60,000 grams per mole, and in some embodiments, fromabout 10,000 to about 40,000 grams per mole. Likewise, the water-solublepolymers may also have a weight average molecular weight (“M_(w)”)ranging from about 10,000 to about 150,000 grams per mole, in someembodiments from about 20,000 to about 100,000 grams per mole, and insome embodiments, from about 30,000 to about 75,000 grams per mole. Theratio of the weight average molecular weight to the number averagemolecular weight (“M_(w)/M_(n)”), i.e., the “polydispersity index”, isalso relatively low. For example, the polydispersity index typicallyranges from about 1.0 to about 4.0, in some embodiments from about 1.1to about 3.0, and in some embodiments, from about 1.2 to about 2.5. Thewater-soluble polymers may also have a solution viscosity of from about50 to about 800 milliPascal seconds (mPa·s), in some embodiments fromabout 100 to about 700 mPa·s, and in some embodiments, from about 200 toabout 600 mPa·s. The solution viscosity is measured as a 4 percentaqueous solution at 20° C. by the Hoeppler falling ball method inaccordance with ASTM-D 1343-56 Part 8, 1958, page 486.

A plasticizer is also employed in the present invention to help renderthe water-soluble polymer melt-processible. Suitable plasticizers mayinclude, for instance, polyhydric alcohol plasticizers, such as sugars(e.g., glucose, sucrose, fructose, raffinose, maltodextrose, galactose,xylose, maltose, lactose, mannose, and erythrose), sugar alcohols (e.g.,erythritol, xylitol, malitol, mannitol, and sorbitol), polyols (e.g.,ethylene glycol, glycerol, propylene glycol, dipropylene glycol,butylene glycol, and hexane trial), etc. Also suitable are hydrogen bondforming organic compounds which do not have hydroxyl group, includingurea and urea derivatives; anhydrides of sugar alcohols such assorbitan; animal proteins such as gelatin; vegetable proteins such assunflower protein, soybean proteins, cotton seed proteins; and mixturesthereof. Other suitable plasticizers may include phthalate esters,dimethyl and diethylsuccinate and related esters, glycerol triacetate,glycerol mono and diacetates, glycerol mono, di, and tripropionates,butanoates, stearates, lactic acid esters, citric acid esters, adipicacid esters, stearic acid esters, oleic acid esters, and other acidesters. Aliphatic acids may also be used, such as copolymers of ethyleneand acrylic acid, polyethylene grafted with maleic acid,polybutadiene-co-acrylic acid, polybutadiene-co-maleic acid,polypropylene-co-acrylic acid, polypropylene-co-maleic acid, and otherhydrocarbon based acids. A low molecular weight plasticizer ispreferred, such as less than about 20,000 g/mol, preferably less thanabout 5,000 g/mol and more preferably less than about 1,000 g/mol.

Typically, the weight ratio of the water-soluble polymer to theplasticizer may be from about 1 to about 50, in some embodiments fromabout 2 to about 25, and in some embodiments, from about 3 to about 15.For example, a blend of plasticizer and water-soluble polymer(“plasticized water-soluble polymer”) may contain from about 1 wt. % toabout 40 wt. %, in some embodiments from about 2 wt. % to about 30 wt.%, and in some embodiments, from about 5 wt % to about 25 wt. % of theplasticizer, and also from about 60 wt. % to about 99 wt. %, in someembodiments from about 70 wt. % to about 98 wt %, and in someembodiments, from about 75 wt. % to about 95 wt. % of the water-solublepolymer.

Through selective control over the nature of the water-soluble polymer(e.g., molecular weight, viscosity, etc.), the nature of theplasticizer, and the relative amounts of the water-soluble polymer andplasticizer, the resulting plasticized water-soluble polymer may achievea melt viscosity that is similar to that of the thermoplasticpolyurethane, which further helps minimize phase separation duringformation of the film. That is, the ratio of the melt viscosity of thethermoplastic polyurethane to the plasticized water-soluble polymer istypically from about 0.01 to about 2.0, in some embodiments from about0.1 to about 1.75, and in some embodiments, from about 0.5 to about 1.5.For example, the plasticized water-soluble polymer may have an apparentmelt viscosity of from about 10 to about 400 Pascal seconds (Pas), insome embodiments from about 20 to about 200 Pa·s, and in someembodiments, from about 30 to about 80 Pa·s, as determined at atemperature of 195° C. and a shear rate of 1000 sec⁻¹. Likewise, theapparent melt viscosity of the thermoplastic polyurethane may range fromabout 20 to about 500 Pascal seconds (Pa·s), in some embodiments fromabout 30 to about 200 Pa·s, and in some embodiments, from about 40 toabout 100 Pa·s, as determined at a temperature of 195° C. and a shearrate of 1000 sec⁻¹.

The relative amount of the water-soluble polymer and thermoplasticpolyurethane employed in the film may also be selected to help furtherminimize phase separation. For example, the weight ratio of thewater-soluble polymer to the thermoplastic polyurethane is typicallyfrom about 0.01 to about 3.0, in some embodiments from about 0.1 toabout 2.5, and in some embodiments, from about 1.0 to about 2.0. Thethermoplastic polyurethane may constitute from about 10 wt. % to about70 wt. %, in some embodiments from about 15 wt. % to about 60 wt. %, andin some embodiments, from about 20 wt. % to about 50 wt. % of the film.The water-soluble polymer may constitute from about 20 wt. % to about 90wt. %, in some embodiments from about 30 wt. % to about 80 wt. %, and insome embodiments, from about 40 wt. % to about 70 wt. % of the film.Likewise, the plasticizer may constitute from about 1 wt. % to about 30wt. %, in some embodiments from about 2 wt. % to about 20 wt. %, and insome embodiments, from about 5 wt. % to about 15 wt. % of the film.

C. Other Components

Other components may also be incorporated into the film as is known inthe art. In one embodiment, for example, the film may include a starch.Although starch is produced in many plants, typical sources includesseeds of cereal grains, such as corn, waxy corn, wheat, sorghum, rice,and waxy rice; tubers, such as potatoes; roots, such as tapioca (i.e.,cassava and manioc), sweet potato, and arrowroot; and the pith of thesago palm. Broadly speaking, native (unmodified) and/or modifiedstarches may be employed. Modified starches, for instance, may beemployed that have been chemically modified by typical processes knownin the art (e.g., esterification, etherification, oxidation, enzymatichydrolysis, etc.). Starch ethers and/or esters may be particularlydesirable, such as hydroxyalkyl starches, carboxymethyl starches, etc.The hydroxyalkyl group of hydroxylalkyl starches may contain, forinstance, 2 to 10 carbon atoms, in some embodiments from 2 to 6 carbonatoms, and in some embodiments, from 2 to 4 carbon atoms. Representativehydroxyalkyl starches such as hydroxyethyl starch, hydroxypropyl starch,hydroxybutyl starch, and derivatives thereof. Starch esters, forinstance, may be prepared using a wide variety of anhydrides (e.g.,acetic, propionic, butyric, and so forth), organic acids, acidchlorides, or other esterification reagents. The degree ofesterification may vary as desired, such as from 1 to 3 ester groups perglucosidic unit of the starch.

Further, the film may also contain one or more biodegradable polyesters.The term “biodegradable” generally refers to a material that degradesfrom the action of naturally occurring microorganisms, such as bacteria,fungi, and algae; environmental heat; moisture; or other environmentalfactors, such as determined according to ASTM Test Method 5338.92.Examples of suitable biodegradable polyesters include aliphaticpolyesters, such as polycaprolactone, polyesteramides, modifiedpolyethylene terephthalate, polylactic acid (PLA) and its copolymers,terpolymers based on polylactic acid, polyglycolic acid, polyalkylenecarbonates (such as polyethylene carbonate), polyhydroxyalkanoates(PHA), poly-3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV),poly-3-hydroxybutyrate-co-4-hydroybutyrate,poly-3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (PHBV),poly-3-hydroxybutyrate-co-3-hydroxyhexanoate,poly-3-hydroxybutyrate-co-3-hydroxyoctanoate,poly-3-hydroxybutyrate-co-3-hydroxydecanoate,poly-3-hydroxybutyrate-co-3-hydroxyoctadecanoate, and succinate-basedaliphatic polymers (e.g., polybutylene succinate, polybutylene succinateadipate, polyethylene succinate, etc.); aromatic polyesters and modifiedaromatic polyesters; and aliphatic-aromatic copolyesters. For example,the biodegradable polyester may be an aliphatic-aromatic copolyesterhaving the following structure:

wherein,

m is an integer from 2 to 10, in some embodiments from 2 to 4, and inone embodiment, 4;

n is an integer from 0 to 18, in some embodiments from 2 to 4, and inone embodiment, 4;

p is an integer from 2 to 10, in some embodiments from 2 to 4, and inone embodiment, 4;

x is an integer greater than 1; and

y is an integer greater than 1. One example of such a copolyester ispolybutylene adipate terephthalate, which is commercially availableunder the designation ECOFLEX® F BX 7011 from BASF Corp. Another exampleof a suitable copolyester containing an aromatic terephtalic acidmonomer constituent is available under the designation ENPOL™ 8060M fromIRE Chemicals (South Korea). Other suitable aliphatic-aromaticcopolyesters may be described in U.S. Pat. Nos. 5,292,783; 5,446,079;5,559,171; 5,580,911; 5,599,858; 5,817,721; 5,900,322; and 6,258,924,which are incorporated herein in their entirety by reference thereto forall purposes.

In addition to the components noted above, other additives may also beincorporated into the film of the present invention, such as slipadditives (e.g., fatty acid salts, fatty acid amides, etc.),compatibilizers (e.g., functionalized polyolefins), dispersion aids,melt stabilizers, processing stabilizers, heat stabilizers, lightstabilizers, antioxidants, heat aging stabilizers, whitening agents,antiblocking agents, bonding agents, lubricants, fillers, etc.Dispersion aids, for instance, may also be employed to help create auniform dispersion of the starch/polyvinyl alcohol/plasticizer mixtureand retard or prevent separation into constituent phases. Likewise, thedispersion aids may also improve the water dispersibility of the film.When employed, the dispersion aid(s) typically constitute from about0.01 wt. % to about 15 wt. %, in some embodiments from about 0.1 wt. %to about 10 wt. %, and in some embodiments, from about 0.5 wt. % toabout 5 wt. % of the film. Although any dispersion aid may generally beemployed in the present invention, surfactants having a certainhydrophilic/lipophilic balance (“HLB”) may improve the long-termstability of the composition. The HLB index is well known in the art andis a scale that measures the balance between the hydrophilic andlipophilic solution tendencies of a compound. The HLB scale ranges from1 to approximately 50, with the lower numbers representing highlylipophilic tendencies and the higher numbers representing highlyhydrophilic tendencies. In some embodiments of the present invention,the HLB value of the surfactants is from about 1 to about 20, in someembodiments from about 1 to about 15 and in some embodiments, from about2 to about 10. If desired, two or more surfactants may be employed thathave HLB values either below or above the desired value, but togetherhave an average HLB value within the desired range.

One particularly suitable class of surfactants for use in the presentinvention are nonionic surfactants, which typically have a hydrophobicbase (e.g., long chain alkyl group or an alkylated aryl group) and ahydrophilic chain (e.g., chain contaiing ethoxy and/or propoxymoieties). For instance, some suitable nonionic surfactants that may beused include, but are not limited to, ethoxylated alkylphenols,ethoxylated and propoxylated fatty alcohols, polyethylene glycol ethersof methyl glucose, polyethylene glycol ethers of sorbitol, ethyleneoxide-propylene oxide block copolymers, ethoxylated esters of fatty(C₈-C₁₈) acids, condensation products of ethylene oxide with long chainamines or amides, condensation products of ethylene oxide with alcohols,fatty acid esters, monoglyceride or diglycerides of long chain alcohols,and mixtures thereof. In one particular embodiment, the nonionicsurfactant may be a fatty acid ester, such as a sucrose fatty acidester, glycerol fatty acid ester, propylene glycol fatty acid ester,sorbitan fatty acid ester, pentaerythritol fatty acid ester, sorbitolfatty acid ester, and so forth. The fatty acid used to form such estersmay be saturated or unsaturated, substituted or unsubstituted, and maycontain from 6 to 22 carbon atoms, in some embodiments from 8 to 18carbon atoms, and in some embodiments, from 12 to 14 carbon atoms. Inone particular embodiment, mono- and di-glycerides of fatty acids may beemployed in the present invention.

Fillers may also be employed in the present invention. Fillers areparticulates or other forms of material that may be added to the filmpolymer extrusion blend and that will not chemically interfere with theextruded film, but which may be uniformly dispersed throughout the film.Fillers may serve a variety of purposes, including enhancing filmopacity and/or breathability (i.e., vapor-permeable and substantiallyliquid-impermeable). For instance, filled films may be made breathableby stretching, which causes the polymer to break away from the fillerand create microporous passageways. Breathable microporous elastic filmsare described, for example, in U.S. Pat. Nos. 5,997,981; 6,015,764; and6,111,163 to McCormack, et al.; 5,932,497 to Morman, et al.; 6,461,457to Taylor, et al., which are incorporated herein in their entirety byreference thereto for all purposes. Further, hindered phenols arecommonly used as an antioxidant in the production of films. Somesuitable hindered phenols include those available from Ciba SpecialtyChemicals under the trade name “Irganox®”, such as Irganox® 1076, 1010,or E 201. Moreover, bonding agents may also be added to the film tofacilitate bonding of the film to additional materials (e.g., nonwovenwebs). Examples of such bonding agents include hydrogenated hydrocarbonresins. Other suitable bonding agents are described in U.S. Pat. Nos.4,789,699 to Kieffer et al. and 5,695,868 to McCormack, which areincorporated herein in their entirety by reference thereto for allpurposes.

II. Film Construction

The film of the present invention may be mono- or multi-layered.Multilayer films may be prepared by co-extrusion of the layers,extrusion coating, or by any conventional layering process. Suchmultilayer films normally contain at least one base layer and at leastone skin layer, but may contain any number of layers desired. Forexample, the multilayer film may be formed from a base layer and one ormore skin layers, wherein the base layer is formed from a blend of thewater-soluble polymer and thermoplastic urethane. In most embodiments,the skin layer(s) are also formed from the blend as described above. Itshould be understood, however, that other polymers may also be employedin the skin layer(s).

Any known technique may be used to form a film from the compoundedmaterial, including blowing, casting, flat die extruding, etc. In oneparticular embodiment, the film may be formed by a blown process inwhich a gas (e.g., air) is used to expand a bubble of the extrudedpolymer blend through an annular die. The bubble is then collapsed andcollected in flat film form. Processes for producing blown films aredescribed, for instance, in U.S. Pat. Nos. 3,354,506 to Raley; 3,650,649to Schippers; and 3,801,429 to Schrenk et al., as well as U.S. PatentApplication Publication Nos. 2005/0245162 to McCormack, et al. and2003/0068951 to Boggs, et al., all of which are incorporated herein intheir entirety by reference thereto for all purposes. In yet anotherembodiment, however, the film is formed using a casting technique.

Referring to FIG. 1, for instance, one embodiment of a method forforming a cast film is shown. The raw materials (e.g., plasticizer,water-soluble polymer, thermoplastic polyurethane, etc.) may be suppliedto a melt blending device, either separately or as a blend. In oneembodiment, for example, the components are separately supplied to amelt blending device where they are dispersively blended in a mannersuch as described above. For example, an extruder may be employed thatincludes feeding and venting ports. In one embodiment, the thermoplasticpolyurethane may be fed to a feeding port of the twin-screw extruder andmelted. Thereafter, the plasticizer and water-soluble polymer may be fedinto the polymer melt. Regardless, the materials are blended under highshear/pressure and heat to ensure sufficient mixing. For example, meltblending may occur at a temperature of from about 75° C. to about 400°C., in some embodiments, from about 80° C. to about 300° C., and in someembodiments, from about 90° C. to about 250° C. Likewise, the apparentshear rate during melt blending may range from about 100 seconds⁻¹ toabout 10,000 seconds⁻¹, in some embodiments from about 500 seconds⁻¹ toabout 5000 seconds⁻¹, and in some embodiments, from about 800 seconds⁻¹to about 1200 seconds⁻¹. The apparent shear rate is equal to 4Q/πR³,where Q is the volumetric flow rate (“m³/s”) of the polymer melt and Ris the radius (“m”) of the capillary (e.g., extruder die) through whichthe melted polymer flows.

Thereafter, the extruded material may be immediately chilled and cutinto pellet form. In the particular embodiment of FIG. 1, the compoundedmaterial (not shown) is then supplied to an extrusion apparatus 80 andcast onto a casting roll 90 to form a single-layered precursor film 10a. If a multilayered film is to be produced, the multiple layers areco-extruded together onto the casting roll 90. The casting roll 90 mayoptionally be provided with embossing elements to impart a pattern tothe film. Typically, the casting roll 90 is kept at temperaturesufficient to solidify and quench the sheet 10 a as it is formed, suchas from about 20 to 60° C. If desired, a vacuum box may be positionedadjacent to the casting roll 90 to help keep the precursor film 10 aclose to the surface of the roll 90. Additionally, air knives orelectrostatic pinners may help force the precursor film 10 a against thesurface of the casting roll 90 as it moves around a spinning roll. Anair knife is a device known in the art that focuses a stream of air at avery high flow rate to pin the edges of the film.

Once cast, the film 10 a may then be optionally oriented in one or moredirections to further improve film uniformity and reduce thickness.Orientation may also form micropores in a film containing a filler, thusproviding breathability to the film. For example, the film may beimmediately reheated to a temperature below the melting point of one ormore polymers in the film, but high enough to enable the composition tobe drawn or stretched. In the case of sequential orientation, the“softened” film is drawn by rolls rotating at different speeds ofrotation such that the sheet is stretched to the desired draw ratio inthe longitudinal direction (machine direction). This “uniaxially”oriented film may then be laminated to a fibrous web. In addition, theuniaxially oriented film may also be oriented in the cross-machinedirection to form a “biaxially oriented” film. For example, the film maybe clamped at its lateral edges by chain clips and conveyed into atenter oven. In the tenter oven, the film may be reheated and drawn inthe cross-machine direction to the desired draw ratio by chain clipsdiverged in their forward travel.

Referring again to FIG. 1, for instance, one method for forming auniaxially oriented film is shown. As illustrated, the precursor film 10a is directed to a film-orientation unit 100 or machine directionorienter (“MDO”), such as commercially available from Marshall andWillams, Co. of Providence, R.I. The MDO has a plurality of stretchingrolls (such as from 5 to 8) which progressively stretch and thin thefilm in the machine direction, which is the direction of travel of thefilm through the process as shown in FIG. 1. While the MDO 100 isillustrated with eight rolls, it should be understood that the number ofrolls may be higher or lower, depending on the level of stretch that isdesired and the degrees of stretching between each roll. The film may bestretched in either single or multiple discrete stretching operations.It should be noted that some of the rolls in an MDO apparatus may not beoperating at progressively higher speeds. If desired, some of the rollsof the MDO 100 may act as preheat rolls. If present, these first fewrolls heat the film 10 a above room temperature (e.g., to 125° F.). Theprogressively faster speeds of adjacent rolls in the MDO act to stretchthe film 10 a. The rate at which the stretch rolls rotate determines theamount of stretch in the film and final film weight.

The resulting film 10 b may then be wound and stored on a take-up roll60. While not shown here, various additional potential processing and/orfinishing steps known in the art, such as slitting, treating,aperturing, printing graphics, or lamination of the film with otherlayers (e.g., nonwoven web materials), may be performed withoutdeparting from the spirit and scope of the invention.

The thickness of the resulting water-sensitive elastic film maygenerally vary depending upon the desired use. Nevertheless, the filmthickness is typically minimized to reduce the time needed for the filmto disperse in water. Thus, in most embodiments of the presentinvention, the water-sensitive elastic film has a thickness of about 50micrometers or less, in some embodiments from about 1 to about 100micrometers, in some embodiments from about 5 to about 75 micrometers,and in some embodiments, from about 10 to about 60 micrometers.

Despite having such a small thickness and good sensitivity in water, thefilm of the present invention is nevertheless able to retain good drymechanical properties during use. One parameter that is indicative ofthe relative dry strength of the film is the ultimate tensile strength,which is equal to the peak stress obtained in a stress-strain curve.Desirably, the film of the present invention exhibits an ultimatetensile strength in the machine direction (“MD”) of from about 10 toabout 80 Megapascals (MPa), in some embodiments from about 15 to about60 MPa, and in some embodiments, from about 20 to about 50 MPa, and anultimate tensile strength in the cross-machine direction (“CD”) of fromabout 2 to about 40 Megapascals (MPa), in some embodiments from about 4to about 40 MPa, and in some embodiments, from about 5 to about 30 MPa.Although possessing good strength, it is also desirable that the film isnot too stiff. One parameter that is indicative of the relativestiffness of the film (when dry) is Young's modulus of elasticity, whichis equal to the ratio of the tensile stress to the tensile strain and isdetermined from the slope of a stress-strain curve. For example, thefilm typically exhibits a Young's modulus in the machine direction(“MD”) of from about 20 to about 800 Megapascals (“MPa”), in someembodiments from about 50 to about 500 MPa, and in some embodiments,from about 100 to about 400 MPa, and a Young's modulus in thecross-machine direction (“CD”) of from about 20 to about 800 Megapascals(“MPa”), in some embodiments from about 50 to about 500 MPa, and in someembodiments, from about 100 to about 400 MPa.

The film is also generally extensible in that it possesses an elongationin the machine and/or cross-machine direction of about 50% or more, insome embodiments about 100% or more, in some embodiments about 200% ormore, and in some embodiments, about 300% or more. Besides beingextensible, the film is also generally elastic in that is capable ofrecovering at least about 50% of its stretched length upon release ofthe stretching force. The elasticity of the film may be characterized byits “percent set”, which is typically about 30% or less, in someembodiments about 15% or less, in some embodiments about 10% or less,and in some embodiments, from about 0.001% to about 5%.

The water-sensitive elastic film of the present invention may be used ina wide variety of applications. For example, as indicated above, thefilm may be used in an absorbent article. An “absorbent article”generally refers to any article capable of absorbing water or otherfluids. Examples of some absorbent articles include, but are not limitedto, personal care absorbent articles, such as diapers, training pants,absorbent underpants, incontinence articles, feminine hygiene products(e.g., sanitary napkins, pantiliners, etc.), swim wear, baby wipes, andso forth; medical absorbent articles, such as garments, fenestrationmaterials, underpads, bed pads, bandages, absorbent drapes, and medicalwipes; food service wipers; clothing articles; and so forth. Severalexamples of such absorbent articles are described in U.S. Pat. Nos.5,649,916 to DiPalma, et al.; 6,110,158 to Kielpikowski; 6,663,611 toBlaney, et al., which are incorporated herein in their entirety byreference thereto for all purposes. Still other suitable articles aredescribed in U.S. Patent Application Publication No. 2004/0060112 A1 toFell et al., as well as U.S. Pat. Nos. 4,886,512 to Damico et al.;5,558,659 to Sherrod et al.; 6,888,044 to Fell et al.; and 6,511,465 toFreiburger et al., all of which are incorporated herein in theirentirety by reference thereto for all purposes. Materials and processessuitable for forming such absorbent articles are well known to thoseskilled in the art.

As is well known in the art, the absorbent article may be provided withadhesives (e.g., pressure-sensitive adhesives) that help removablysecure the article to the crotch portion of an undergarment and/or wrapup the article for disposal. Suitable pressure-sensitive adhesives, forinstance, may include acrylic adhesives, natural rubber adhesives,tackified block copolymer adhesives, polyvinyl acetate adhesives,ethylene vinyl acetate adhesives, silicone adhesives, polyurethaneadhesives, thermosettable pressure-sensitive adhesives, such as epoxyacrylate or epoxy polyester pressure-sensitive adhesives, etc. Suchpressure-sensitive adhesives are known in the art and are described inthe Handbook of Pressure Sensitive Adhesive Technology, Satas (Donatas),1989, 2^(nd) edition, Van Nostrand Reinhold. The pressure sensitiveadhesives may also include additives such as cross-linking agents,fillers, gases, blowing agents, glass or polymeric microspheres, silica,calcium carbonate fibers, surfactants, and so forth. The additives areincluded in amounts sufficient to affect the desired properties.

The location of the adhesive on the absorbent article is not criticaland may vary widely depending on the intended use of the article. Forexample, certain feminine hygiene products (e.g., sanitary napkins) mayhave wings or flaps that extend laterally from a central absorbent coreand are intended to be folded around the edges of the wearer's pantiesin the crotch region. The flaps may be provided with an adhesive (e.g.,pressure-sensitive adhesive) for affixing the flaps to the underside ofthe wearer's panties.

Regardless of the particular location of the adhesive, however, arelease liner may be employed to cover the adhesive, thereby protectingit from dirt, drying out, and premature sticking prior to use. Therelease liner may contain a release coating that enhances the ability ofthe liner to be peeled from an adhesive. The release coating contains arelease agent, such as a hydrophobic polymer. Exemplary hydrophobicpolymers include, for instance, silicones (e.g., polysiloxanes, epoxysilicones, etc.), perfluoroethers, fluorocarbons, polyurethanes, and soforth. Examples of such release agents are described, for instance, inU.S. Pat. Nos. 6,530,910 to Pomplun, et al.; 5,985,396 to Kerins, etal.; and 5,981,012 to Pomplun, et al., which are incorporated herein intheir entirety by reference thereto for all purposes. One particularlysuitable release agent is an amorphous polyolefin having a meltviscosity of about 400 to about 10,000 cps at 190° C., such as made bythe U.S. Rexene Company under the tradename REXTAC® (e.g., RT2315,RT2535 and RT2330). The release coating may also contain a detackifier,such as a low molecular weight, highly branched polyolefin. Aparticularly suitable low molecular weight, highly branched polyolefinis VYBAR® 253, which is made by the Petrolite Corporation. Otheradditives may also be employed in the release coating, such ascompatibilizers, processing aids, plasticizers, tackifiers, slip agents,and antimicrobial agents, and so forth. The release coating may beapplied to one or both surfaces of the liner, and may cover all or onlya portion of a surface. Any suitable technique may be employed to applythe release coating, such as solvent-based coating, hot melt coating,solventless coating, etc. Solvent-based coatings are typically appliedto the release liner by processes such as roll coating, knife coating,curtain coating, gravure coating, wound rod coating, and so forth. Thesolvent (e.g., water) is then removed by drying in an oven, and thecoating is optionally cured in the oven. Solventless coatings mayinclude solid compositions, such as silicones or epoxy silicones, whichare coated onto the liner and then cured by exposure to ultravioletlight. Optional steps include priming the liner before coating orsurface modification of the liner, such as with corona treatment. Hotmelt coatings, such as polyethylenes or perfluoroethers, may be heatedand then applied through a die or with a heated knife. Hot melt coatingsmay be applied by co-extruding the release agent with the release linerin blown film or sheet extruder for ease of coating and for processefficiency.

To facilitate its ability to be easily disposed, the release liner maybe formed from a water-sensitive film in accordance with the presentinvention. In this regard, one particular embodiment of a sanitarynapkin that may employ the water-sensitive film will now be described inmore detail. For purposes of illustration only, an absorbent article 20is shown in FIG. 2 as a sanitary napkin for feminine hygiene. In theillustrated embodiment, the absorbent article 20 includes a main bodyportion 22 containing a topsheet 40, an outer cover or backsheet 42, anabsorbent core 44 positioned between the backsheet 42 and the topsheet40, and a pair of flaps 24 extending from each longitudinal side 22 a ofthe main body portion 22. The topsheet 40 defines a bodyfacing surfaceof the absorbent article 20. The absorbent core 44 is positioned inwardfrom the outer periphery of the absorbent article 20 and includes abody-facing side positioned adjacent the topsheet 40 and agarment-facing surface positioned adjacent the backsheet 42. Thetopsheet 40 is generally designed to contact the body of the user and isliquid-permeable. The topsheet 40 may surround the absorbent core 44 sothat it completely encases the absorbent article 20. Alternatively, thetopsheet 40 and the backsheet 42 may extend beyond the absorbent core 44and be peripherally joined together, either entirely or partially, usingknown techniques. Typically, the topsheet 40 and the backsheet 42 arejoined by adhesive bonding, ultrasonic bonding, or any other suitablejoining method known in the art. The topsheet 40 is sanitary, clean inappearance, and somewhat opaque to hide bodily discharges collected inand absorbed by the absorbent core 44. The topsheet 40 further exhibitsgood strike-through and rewet characteristics permitting bodilydischarges to rapidly penetrate through the topsheet 40 to the absorbentcore 44, but not allow the body fluid to flow back through the topsheet40 to the skin of the wearer. For example, some suitable materials thatmay be used for the topsheet 40 include nonwoven materials, perforatedthermoplastic films, or combinations thereof. A nonwoven fabric madefrom polyester, polyethylene, polypropylene, bicomponent, nylon, rayon,or like fibers may be utilized. For instance, a white uniform spunbondmaterial is particularly desirable because the color exhibits goodmasking properties to hide menses that has passed through it. U.S. Pat.No. 4,801,494 to Datta, et al. and U.S. Pat. No. 4,908,026 to Sukiennik,et al. teach various other cover materials that may be used in thepresent invention.

The topsheet 40 may also contain a plurality of apertures (not shown)formed therethrough to permit body fluid to pass more readily into theabsorbent core 44. The apertures may be randomly or uniformly arrangedthroughout the topsheet 40, or they may be located only in the narrowlongitudinal band or strip arranged along the longitudinal axis X-X ofthe absorbent article 20. The apertures permit rapid penetration of bodyfluid down into the absorbent core 44. The size, shape, diameter andnumber of apertures may be varied to suit one's particular needs.

As stated above, the absorbent article also includes a backsheet 42. Thebacksheet 42 is generally liquid-impermeable and designed to face theinner surface, i.e., the crotch portion of an undergarment (not shown).The backsheet 42 may permit a passage of air or vapor out of theabsorbent article 20, while still blocking the passage of liquids. Anyliquid-impermeable material may generally be utilized to form thebacksheet 42. For example, one suitable material that may be utilized isa microembossed polymeric film, such as polyethylene or polypropylene.In particular embodiments, a polyethylene film is utilized that has athickness in the range of about 0.2 mils to about 5.0 mils, andparticularly between about 0.5 to about 3.0 mils.

The absorbent article 20 also contains an absorbent core 44 positionedbetween the topsheet 40 and the backsheet 42. The absorbent core 44 maybe formed from a single absorbent member or a composite containingseparate and distinct absorbent members. It should be understood,however, that any number of absorbent members may be utilized in thepresent invention. For example, in one embodiment, the absorbent core 44may contain an intake member (not shown) positioned between the topsheet40 and a transfer delay member (not shown). The intake member may bemade of a material that is capable of rapidly transferring, in thez-direction, body fluid that is delivered to the topsheet 40. The intakemember may generally have any shape and/or size desired. In oneembodiment, the intake member has a rectangular shape, with a lengthequal to or less than the overall length of the absorbent article 20,and a width less than the width of the absorbent article 20. Forexample, a length of between about 150 mm to about 300 mm and a width ofbetween about 10 mm to about 60 mm may be utilized.

Any of a variety of different materials may be used for the intakemember to accomplish the above-mentioned functions. The material may besynthetic, cellulosic, or a combination of synthetic and cellulosicmaterials. For example, airlaid cellulosic tissues may be suitable foruse in the intake member. The airlaid cellulosic tissue may have a basisweight ranging from about 10 grams per square meter (gsm) to about 300gsm, and in some embodiments, between about 100 gsm to about 250 gsm. Inone embodiment, the airlaid cellulosic tissue has a basis weight ofabout 200 gsm. The airlaid tissue may be formed from hardwood and/orsoftwood fibers. The airlaid tissue has a fine pore structure andprovides an excellent wicking capacity, especially for menses.

If desired, a transfer delay member (not shown) may be positionedvertically below the intake member. The transfer delay member maycontain a material that is less hydrophilic than the other absorbentmembers, and may generally be characterized as being substantiallyhydrophobic. For example, the transfer delay member may be a nonwovenfibrous web composed of a relatively hydrophobic material, such aspolypropylene, polyethylene, polyester or the like, and also may becomposed of a blend of such materials. One example of a materialsuitable for the transfer delay member is a spunbond web composed ofpolypropylene, multi-lobal fibers. Further examples of suitable transferdelay member materials include spunbond webs composed of polypropylenefibers, which may be round, tri-lobal or poly-lobal in cross-sectionalshape and which may be hollow or solid in structure. Typically the websare bonded, such as by thermal bonding, over about 3% to about 30% ofthe web area. Other examples of suitable materials that may be used forthe transfer delay member are described in U.S. Pat. No. 4,798,603 toMeyer, et al. and U.S. Pat. No. 5,248,309 to Serbiak, et al., which areincorporated herein in their entirety by reference thereto for allpurposes. To adjust the performance of the invention, the transfer delaymember may also be treated with a selected amount of surfactant toincrease its initial wettability.

The transfer delay member may generally have any size, such as a lengthof about 150 mm to about 300 mm. Typically, the length of the transferdelay member is approximately equal to the length of the absorbentarticle 20. The transfer delay member may also be equal in width to theintake member, but is typically wider. For example, the width of thetransfer delay member may be from between about 50 mm to about 75 mm,and particularly about 48 mm. The transfer delay member typically has abasis weight less than that of the other absorbent members. For example,the basis weight of the transfer delay member is typically less thanabout 150 grams per square meter (gsm), and in some embodiments, betweenabout 10 gsm to about 100 gsm. In one particular embodiment, thetransfer delay member is formed from a spunbonded web having a basisweight of about 30 gsm.

Besides the above-mentioned members, the absorbent core 44 may alsoinclude a composite absorbent member (not shown), such as a coformmaterial. In this instance, fluids may be wicked from the transfer delaymember into the composite absorbent member. The composite absorbentmember may be formed separately from the intake member and/or transferdelay member, or may be formed simultaneously therewith. In oneembodiment, for example, the composite absorbent member may be formed onthe transfer delay member or intake member, which acts a carrier duringthe coform process described above.

Regardless of its particular construction, the absorbent article 20typically contains an adhesive for securing to an undergarment. Anadhesive may be provided at any location of the absorbent article 20,such as on the lower surface of the backsheet 42. In this particularembodiment, the backsheet 42 carries a longitudinally central strip ofgarment adhesive 54 covered before use by a peelable release liner 58,which may be formed in accordance with the present invention. Each ofthe flaps 24 may also contain an adhesive 56 positioned adjacent to thedistal edge 34 of the flap 24. A peelable release liner 57, which mayalso be formed in accordance with the present invention, may cover theadhesive 56 before use. Thus, when a user of the sanitary absorbentarticle 20 wishes to expose the adhesives 54 and 56 and secure theabsorbent article 20 to the underside of an undergarment, the usersimply peels away the liners 57 and 58 and disposed them in awater-based disposal system (e.g., in a toilet).

Although various configurations of a release liner have been describedabove, it should be understood that other release liner configurationsare also included within the scope of the present invention. Further,the present invention is by no means limited to release liners and thewater-sensitive elastic film may be incorporated into a variety ofdifferent components of an absorbent article. For example, referringagain to FIG. 2, the backsheet 42 of the napkin 20 may include thewater-sensitive film of the present invention. In such embodiments, thefilm may be used alone to form the backsheet 42 or laminated to one ormore additional materials, such as a nonwoven web. The water-sensitiveelastic film of the present invention may also be used in applicationsother than absorbent articles. For example, the film may be employed asan individual wrap, packaging pouch, or bag for the disposal of avariety of articles, such as food products, absorbent articles, etc.Various suitable pouch, wrap, or bag configurations for absorbentarticles are disclosed, for instance, in U.S. Pat. Nos. 6,716,203 toSorebo, et al. and 6,380,445 to Moder, et al., as well as U.S. PatentApplication Publication No. 2003/0116462 to Sorebo, et al., all of whichare incorporated herein in their entirety by reference thereto for allpurposes.

The present invention may be better understood with reference to thefollowing examples.

Test Methods

Apparent Melt Viscosity:

The rheological properties of polymer samples were determined using aGöttfert Rheograph 2003 capillary rheometer with WinRHEO version 2.31analysis software. The setup included a 2000-bar pressure transducer anda 30/1:0/180 roundhole capillary die. Sample loading was done byalternating between sample addition and packing with a ramrod. A2-minute melt time preceded each test to allow the polymer to completelymelt at a test temperature (150° C. or 160° C.). The capillary rheometerdetermined the apparent melt viscosity (Pa·s) at various shear rates,such as 100, 200, 500, 1000, 2000, and 4000 s⁻¹. The resultant rheologycurve of apparent shear rate versus apparent melt viscosity gave anindication of how the polymer would run at that temperature in anextrusion process.

Tensile Properties:

The strip tensile strength values were determined in substantialaccordance with ASTM Standard D-5034. A constant-rate-of-extension typeof tensile tester was employed. The tensile testing system was a Sintech1/D tensile tester, which is available from Sintech Corp. of Cary, N.C.The tensile tester was equipped with TESTWORKS 4.08B software from MTSCorporation to support the testing. An appropriate load cell wasselected so that the tested value fell within the range of 10-90% of thefull scale load. The film samples were initially cut into dog-boneshapes with a center width of 3.0 mm before testing. The samples wereheld between grips having a front and back face measuring 25.4millimeters x 76 millimeters. The grip faces were rubberized, and thelonger dimension of the grip was perpendicular to the direction of pull.The grip pressure was pneumatically maintained at a pressure of 40pounds per square inch. The tensile test was run using a gauge length of18.0 millimeters and a break sensitivity of 40%. Five samples weretested by applying the test load along the machine-direction and fivesamples were tested by applying the test load along the cross direction.During the test, samples were stretched at a crosshead speed of abut 127millimeters per minute until breakage occurred. The modulus, peakstress, and elongation were measured in the machine direction (“MD”) andcross-machine directions (“CD”).

Water Disintegration Test:

The rate of film disintegration in tap water was tested using a “sloshbox”, which has a physical dimension of a 14″×18″×12″ high plastic boxon a hinged platform. One end of the platform is attached to thereciprocating cam. The typical amplitude is ±2″ (4″ range), withsloshing occurring at 0.5-1.5 sloshes per second. The preferred actionis 0.9-1.3 sloshes per second. During a test, the slosh box rocks up anddown with the water inside, “sloshing” back and forth. This actionproduces a wave front and intermittent motion on a sample susceptible todispersing in water. To quantify a measurement of sample filmdisintegration in water, without image analysis, simply timing issufficient. Three liters of tap water were added into the slosh box andresulted in ˜5.5″ water depth in the box. A frequency of 3.5 wasselected for the testing. Each film sample was cut into 1″×3″ size.Three pieces were dropped into the slosh box. The time to disintegratethe sample under the defined conditions was recorded twice for eachsample. The average of the time to the sample disintegration is thenreported. Generally, films reach an acceptable dispersion point when nopiece is larger than 25 mm² in size within 6 hours of agitation.

Cycle Testing

The materials were tested using a cyclical testing procedure todetermine percent set. In particular, 1-cycle testing was utilized to100% defined elongation. The testing was done on a Sintech Corp.constant rate of extension tester 1/D equipped with TESTWORKS 4.08Bsoftware from MTS Corporation to support the testing. The test wasconducted under ambient conditions. For this test, the sample size was 1inches (2.54 centimeters) in the cross-machine direction by 3 inches(7.6 centimeter) in the machine direction. The grip size was 3 inches(7.6 centimeters) in width and the grip separation was 4 inches. Thesamples were loaded such that the machine direction of the sample was inthe vertical direction. A preload of approximately 20 to 30 grams wasset. The test pulled the sample to 100% elongation at a speed of 20inches (50.8 centimeters) per minute, held the sample in an elongatedstate for 30 seconds, and then returned the sample to zero elongation ata speed of 20 inches (50.8 centimeters) per minute. Thereafter, the filmlength was immediately measured and again measured in 10, 20, and 30minutes. The percent that did not recover (“percent set”) was determinedby subtracting the length of the film 30 minutes after cycle testingfrom the original length of the film, and then dividing this number bythe original length of the film.

EXAMPLE 1

A blend was formed 42 wt. % of a water-soluble polymer, 30 wt. % of anelastomer, and 18 wt. % of plasticizer. The water-soluble polymer wasCELVOL™ 523S (polyvinyl alcohol, Celanese). The elastomer was ESTANE™58245, an aromatic, polyether-based thermoplastic polyurethane availablefrom Lubrizol. The plasticizer was glycerin (Cognis Corporation,Cincinnati, Ohio). These components were fed into a co-rotating twinscrew extruder (ZSK-30, Werner and Pfleiderer Corporation, Ramsey,N.J.). In addition, 10 wt. % calcium carbonate (2sst CaCO₃ from Omya,Alpharetta, Ga.) was fed through the side ⅔ of distance away from thefirst zone. The extruder diameter was 30 mm and the length of the screwswas up to 1328 mm. The extruder has 14 barrels, numbered consecutively 1to 14 from the feed hopper to the die. The temperature profile of zones1 to 14 of the extruder was 110° C., 130° C., 190° C., 190° C., 190° C.,180° C., and 170° C., respectively. The screw speed was set at 150 rpmto achieve a torque of between 45˜50%, P_(melt) of 130˜200 psi, and anoutput of about 18 to 20 lb/hr. The resulting film exhibited flow lines,which generally indicated that the materials were incompatible. The filmhad a thickness of about 0.002 inches.

EXAMPLE 2

A blend was formed 42 wt% of a water-soluble polymer, 30 wt.% of anelastomer, and 18 wt % of plasticizer. The water-soluble polymer wasCELVOL™523S (polyvinyl alcohol, Celanese). The elastomer wasESTANE™58245, an aromatic, polyether-based thermoplastic polyurethaneavailable from Lubrizol. The plasticizer was glycerin (CognisCorporation, Cincinnati, Ohio), These components were fed into aco-rotating twin screw extruder (ZSK-30, Werner and PfleidererCorporation, Ramsey, New Jersey). In addition, 10 wt.% MP 30-36 talc(Barretts Minerals, Dillon, Montana) was fed through the side two-thirdsof the total distance from the first zone. The extruder diameter was30mm and the length of the screws was up to 1328 mm. The extruder has14barrels, numbered consecutively 1 to 14 from the feed hopper to thedie. The temperature profile of zones 1 to 14 of the extruder was 110°C., 130° C., 190° C., 190° C., 190° C., 180° C., and 170° C.,respectively. The screw speed was set at 150rpm to achieve a torque ofbetween 45˜50%, P_(melt) of 130-200 psi, and an output of about 18 to 20lb/hr. The strand skin was rough and showed incompatibility. No filmswere made from the blend.

EXAMPLE 3

A blend was formed 42 wt. % of a water-soluble polymer, 40 wt. % of anelastomer, and 18 wt. % of a plasticizer. The water-soluble polymer wasELVANOL™ 51-05 (polyvinyl alcohol, DuPont). The elastomer was ESTANE™58245, an aromatic, polyether-based thermoplastic polyurethane availablefrom Lubrizol. The plasticizer was sorbitol (Glenn Corporation, WhiteBear Lake, Minn.). The resulting film was rigid and had a thickness ofabout 0.005 inches.

EXAMPLE 4

A blend was formed 50 wt. % of a water-soluble polymer, 20 wt. % of anelastomer, 15 wt. % of a plasticizer, 10 wt. % MP 30-36 (talc), and 5wt. % of FUSABOND™ MC 190D (compatibilizer). The water-soluble polymerwas CELVOL™ 523S (polyvinyl alcohol, Celanese). The elastomer wasESTANE™ 58245, an aromatic, polyether-based thermoplastic polyurethaneavailable from Lubrizol. The plasticizer was glycerin (CognisCorporation, Cincinnati, Ohio). The strand improved during compounding,but no film was formed.

EXAMPLE 5

A blend was formed 55 wt. % of a water-soluble polymer, 25 wt. % of anelastomer, and 20 wt. % of a plasticizer. The water-soluble polymer wasCELVOL™ 523S (polyvinyl alcohol, Celanese). The elastomer was DESMOPAN™DP 9370A, a polyether-based thermoplastic polyurethane from BayerMaterial Science of Pittsburgh, Pa. The plasticizer used was glycerin(Cognis Corporation, Cincinnati, Ohio). With these materials, pelletswere made from the compounding process. However, the pellets did nothave the processability required to make a film.

EXAMPLE 6

A blend was formed 60 wt. % of a water-soluble polymer, 25 wt. % of anelastomer, and 15 wt. % of a plasticizer. The water-soluble polymer wasCELVOL™ 513 (polyvinyl alcohol, Celanese). The elastomer was DESMOPAN™DP 9370A, a polyether-based thermoplastic polyurethane from BayerMaterial Science of Pittsburgh, Pa. The plasticizer was glycerin (CognisCorporation, Cincinnati, Ohio). With these materials, pellets wereobtained during compounding, although no film was formed.

EXAMPLE 7

A plasticized PVOH was formed from ELVANOL™ 51-05 (DuPont), which wasobtained by feeding 85 wt. % PVOH powder into a co-rotating twin screwextruder (ZSK-30, Werner and Pfleiderer Corporation, Ramsey, N.J.).Glycerin (Cognis Corporation, Cincinnati, Ohio) was used as aplasticizer that was fed at 15 wt % into the zone 1 by an Eldex pump.The extruder diameter was 30 mm and the length of the screws was up to1328 mm. The extruder has 14 barrels, numbered consecutively 1 to 14from the feed hopper to the die. The temperature profile of zones 1 to14 of the extruder was 95° C., 145° C., 185° C., 185° C., 175° C., 160and 155° C., respectively. The screw speed was set at 150 rpm to achievea torque of between 50˜55%, P_(melt) of 180-190 psi, and an output ofabout 19 lb/hr.

EXAMPLES 8-9

The plasticized PVOH from Example 7 was used to blend with DESMOPAN™ DP9370A (Bayer Material Science of Pittsburgh, Pa.) to create a waterresponsive resin. More specifically, plasticized PVOH from Example 7(feeding rate: 12 lbs/hr) and DESMOPAN™ DP 9370A (feeding rate: 8lbs/hr) were respectively fed into a co-rotating twin screw extruder(ZSK-30, Werner and Pfleiderer Corporation, Ramsey, N.J.). Twogravimetric K-Iron feeders were used (K-Tron America, Inc., Pitman,N.J.). The vent at the end of the extruder was open to release somemoisture. A 3-hole die of 3 mm diameter that is separated by 10 mm spacewas used to shape the melt into strands that were cooled on a conveyerbelt and then pelletized. The temperature profile of zones 1 to 14 ofthe extruder was 140° C., 160° C., 170° C., 180° C., 180° C., 170° C.,and 160° C., respectively. The other conditions used to plasticize theELVANOL™ 51-05 (Example 7) and to compound the plasticized polymer withDESMOPAN™ DP 9370A (Examples 8-9) are set forth below in Table 1.

TABLE 1 Processing Conditions Total Material Desmopan Elvanol ExtruderMelt Feed Rate DP 9370A 51-05 Glycerin Speed Pmelt Torque temperatureEx. (lb/hr) (wt. %) (wt. %) (wt. %) (rpm) (psi) (%) (° C.) 7 19 — 85.015.0 150 180-190 50-55 198 8 20 40 51.0 9.0 150 190-240 66-71 164 9 2030 59.5 10.5 150 230-260 72-80 164

The strands from these blends were smooth, which generally indicatedgood resin compatibility. The blends of Examples 8-9 were then providedto a HAAKE Rheomex 252 single screw extruder for film casting. The screwspeed was set at 45 to 55 rpm and the temperature profile of theextruder from zone 1 to 5 was 200° C., 200° C., 205° C., 197° C., and187° C., respectively. The melt temperature was 204° C. to 209° C., thetorque was 1500 to 2000 m-g, and the die pressure was 1100 to 1500 psi.The resulting films had a thickness of about 0.002 inches(˜50.8-micrometers). In some cases, a release paper was introduced tothe first chill roll.

EXAMPLE 10

A film was formed from the blend of Example 7 as described above.

EXAMPLE 11

The mechanical properties of the films of Examples 8-10 were tested asdescribed above. The results are shown in Table 2.

TABLE 2 Thermoplastic Film Mechanical Tensile Properties Film ThicknessPeak Stress (MPa) Elongation (%) Modulus (MPa) Example SampleDescription Composition MD (mil) CD (mil) MD CD MD CD MD CD 8p-Elvanol/Desmopan 60/40 2.2 2.1 26 21 368 349 74 74 9p-Elvanol/Desmopan 70/30 2.2 2.0 37 25 317 280 216 147 10 p-Elvanol85/15 1.1 1.0 48 46 173 161 1224 1554 (Elvanol 51-05/Glycerin)

The modulus of the film of Example 8 was low, indicating that it wasflexible and soft. The plasticized ELVANOL™ 51-05 film of Example 10showed the highest modulus and peak stress, indicating a rigid film.With the presence of an elastomer in the blends (Examples 8 and 9), thefilm elongation was generally greater than that for the plasticizedELVANOL™ 51-05.

EXAMPLE 12

The films of Examples 8-10 were subjected to the above-described waterdisintegration test. The results are set forth below in Table 3.

TABLE 3 Film Disintegration Time Time (min.) Water To First To 25 mm2Temp. Break pieces Run (C.) RPM (min.) (sec.) (min.) (sec.) Example 8p-Elvanol/Desmopan (60/40) 1 23.6 26 1 5.00 4 16.00 2 23.6 26 0 58.00 334.00 Example 9 p-Elvanol/Desmopan (70/30) 1 23.6 26 0 33.00 0 55.00 223.6 26 0 35.00 0 58.00 Example 10 p-Elvanol 1 23.6 26 0 13.00 0 40.00 223.6 26 0 7.00 0 25.00

As indicated, the film of Example 8 began to disperse after about 1minute and broke into two pieces in just over 3 to 4 minutes. As theelastomer content decreased to 30% in Example 9, the time needed for thefilm to disperse was less than one minute, which was comparable to theplasticized ELVANOL™ 51-05 film of Example 10. In general, once thesamples were placed in water, they started to change color.

EXAMPLE 13

To assess elasticity, the films of Examples 8-10 were subjected to cycletesting as described above. Before testing, the net gauge film lengthwas 51 millimeters. The results are set forth below in Table 4.

TABLE 4 Film Mechanical Stretch and Recovery Testing Example SampleDescription Original After Test After 10 min After 20 min After 30 min %Not Recovered 8 p-Elvanol/Desmopan (60/40) - MD 51 58 54 53 53 3.9p-Elvanol/Desmopan (60/40) - CD 51 57 52 51 51 0.0 9 p-Elvanol/Desmopan(70/30) - MD 51 71 55 53 53 3.9 p-Elvanol/Desmopan (70/30) - CD 51 69 5554 53 3.9 10 p-Elvanol (100%) - MD 51 97 85 84 84 64.7 p-Elvanol(100%) - CD 51 N/A N/A N/A N/A N/A

EXAMPLE 14

A scanning electron microscopy (SEM) photograph was taken of the film ofExample 8. The photograph was obtained by plasma etching/optical methodusing the standard secondary electron imaging mode achieved by apositive-biased Everhart-Thornley detector. The results are shown inFIG. 3. As indicated, the film of Example 8 exhibited a substantiallycontinuous phase with a finely distributed elastomer phase showing goodcompatibility between PVOH and polyurethane, which can be easilyaccessed by water to induce disintegration.

EXAMPLE 15

The melt viscosity was determined for plasticized Elvanol™ 51-05,Celvol™ 523S, Celvol™ 513, Desmopan™ DP9370A, and Estane™ 58245 using aGottfert Rhoegraph 2003 capillary rheometer. The results are shown inFIG. 4. For comparative purposes, a shear rate of 1000 s⁻¹ was alsoselected to calculate ratios of the plasticized PVOH or starch-basedblend to Estane™ 58245 or Desmopan™ DP9370A, respectively. These valuesare tabulated in Table 5.

TABLE 5 The Ratio of Plasticized PVOH to Thermoplastic PolyurethanesApparent Viscosity (Pa-S) Shear Rate Desmpopan (s⁻¹) p-Celvol 513p-Celvol 523S p-Elvanol 51-05 Estane 58245 DP9370A 1000 97 114 42 470 59Viscosity Examples 1, Ratio 2, and 3 Example 5 Example 6 Example 8Example 9 <0.2 1.9 1.6 0.7 0.7

The preferred ratio for generating water-sensitive films was from 0.5 to1.5.

While the invention has been described in detail with respect to thespecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereto.

What is claimed is:
 1. A water-sensitive elastic film comprising: atleast one water-soluble polymer, wherein the water-soluble polymer has aweight average molecular weight of from about 10,000 to about 150,000grams per mole and a number average molecular weight of from about 1,000to about 80,000 grams per mole; at least one plasticizer, wherein theweight ratio of the water-soluble polymer to the plasticizer is fromabout 1 to about 50; and at least one thermoplastic polyurethanesynthesized from at least one polyol and at least one organicdiisocyanate, wherein the weight ratio of the water-soluble polymer tothe thermoplastic polyurethane is from about 0.1 to about 2.5 andwherein the melt viscosity ratio of the thermoplastic polyurethane to aplasticized water-soluble polymer is from about 0.1 to about 1.75. 2.The film of claim 1, wherein the water-soluble polymer includes vinylpyrrolidone, hydroxyethyl acrylate or methacrylate, hydroxypropylacrylate or methacrylate, acrylic or methacrylic acid, acrylic ormethacrylic esters or vinyl pyridine, acrylamide, vinyl acetate, vinylalcohol, ethylene oxide, or a combination thereof.
 3. The film of claim1, wherein the water-soluble polymer includes a vinyl alcohol polymer.4. The film of claim 1, wherein the vinyl alcohol polymer has a degreeof hydrolysis of from about 80 mole % to about 90 mole %.
 5. The film ofclaim 1, wherein the water-soluble polymer has a weight averagemolecular weight of from about 30,000 to about 75,000 grams per mole anda number average molecular weight of from about 10,000 to about 40,000grams per mole.
 6. The absorbent article film of claim 1, wherein thewater-soluble polymer has a solution viscosity of from about 50 to about800 milliPascal seconds, as determined in a 4% aqueous solution at 20°C.
 7. The film of claim 1, wherein the water-soluble polymer has asolution viscosity of from about 200 to about 600 milliPascal seconds,as determined in a 4% aqueous solution at 20° C.
 8. The film of claim 1,wherein the ratio of the melt viscosity of the thermoplasticpolyurethane to the plasticized water-soluble polymer is from about 0.5to about 1.5.
 9. The film of claim 1, wherein the plasticizer includes apolyhydric alcohol.
 10. The film of claim 1, wherein the polyhydricalcohol includes a sugar alcohol.
 11. The film of claim 1, wherein theweight ratio of the water-soluble polymer to the plasticizer is fromabout 3 to about
 15. 12. The film of claim 1, wherein the plasticizerconstitutes from about 1 wt. % to about 30 wt. % of the film and thewater-soluble polymer constitutes from about 20 wt. % to about 90 wt. %of the film.
 13. The film of claim 1, wherein the polyol includes apolyether polyol and the organic diisocyanate includes an aromaticdiisocyanate.
 14. The film of claim 1, wherein the thermoplasticpolyurethane has a melting point of from about 75° C. to about 250° C.and a glass transition temperature of from about −150° C. to about 0° C.15. The film of claim 1, wherein the weight ratio of the water-solublepolymer to the thermoplastic polyurethane is from about 1.0 to about2.0.
 16. The film of claim 1, wherein the thermoplastic polyurethaneconstitutes from about 10 wt. % to about 70 wt. % of the film.
 17. Thefilm of claim 1, wherein the film has an elongation of about 100% ormore in the machine direction, cross-machine direction, or both.
 18. Theabsorbent article film of claim 1, wherein the film has a percent set ofabout 30% or less.
 19. An absorbent article comprising thewater-sensitive elastic film of claim
 1. 20. A .method for forming awater-sensitive elastic film, the method comprising: melt blending acomposition comprising at least one water-soluble polymer, wherein thewater-soluble polymer has a weight average molecular weight of fromabout 10,000 to about 150,000 grams per mole and a number averagemolecular weight of from about 1,000 to about 80,000grams per mole; atleast one plasticizer, wherein the weight ratio of the water-solublepolymer to the plasticizer is from about 1 to about 50; and at least onethermoplastic polyurethane synthesized from at least one polyol and atleast one organic diisocyanate, wherein the weight ratio of thewater-soluble polymer to the thermoplastic polyurethane is from about0.1 to about 2.5 and wherein the melt viscosity ratio of thethermoplastic polyurethane to a plasticized water-soluble polymer isfrom about 0.1 to about 1.75; and extruding the composition onto asurface to form a film.
 21. The method of claim 20, further comprisingstretching the film in the machine direction, the cross-machinedirection, or both.